The present invention relates to a device for treating an aneurysm. More specially, the present invention relates to an aneurysm liner expandable from a collapsed profile for deployment in an aneurysm sac.
An aneurysm is a localized stretching or distension of a vessel due to a weakening of the vessel wall. For example, “berry” aneurysms, i.e., small spherical distensions, occur in the vessels of the brain. The distensions—often referred to as the aneurysm sac—are related to defects on the muscular coating of the artery or vessel and are probably degenerative in origin. Rupture of aneurysms accounts for the majority of the spontaneous hemorrhages. Approximately 25,000 intracranial aneurysms rupture every year in North America.
Several methods for treating aneurysms have been attempted, with varying degrees of success. At present, the treatment of aneurysms with drugs is substantially ineffective. Also, extra-vascular surgery, referred to as open craniotomy, for the purpose of preserving the parent artery is replete with disadvantages. A patient subject to open craniotomy for intercranial aneurysms typically must undergo general anesthesia, surgical removal of part of the skull, brain retraction, dissection around the neck of the sac, and placement of a clip on the parent artery to prevent bleeding or rebleeding.
Alternative treatments include endovascular occlusion where the interior of the aneurysm is entered with a guidewire or a microcatheter. An occlusion is formed within the sac with an intention to preserve the parent artery. A preferred means for forming a mass in an aneurysm sac is through the introduction of an embolic agent within the sac. Examples of embolic agents include a detachable coil, which is detached from the end of a guidewire, and a liquid polymer which polymerizes rapidly on contact with blood to form a firm mass. Endovascular occlusion is not without drawbacks. For example, there is a risk of overfilling the sac which can cause embolic agent to migrate from the aneurysm sac into the parent vessel and can create additional pressure in the aneurysm.
Another means for forming a mass in the aneurysm sac involves the placement of an expandable balloon or liner in the aneurysm. Detachable occlusion balloons have been used for a number of medical procedures. These balloons are carried at the end of a and, once inflated can be detached from the catheter. Such a balloon may be positioned within an aneurysm, filled and then detached from the catheter. Deploying an expandable balloon within the aneurysm can be rather difficult due to the high rates of blood flow through the aneurysm.
The balloon must be sufficiently inflated to fill the aneurysm so that it does not migrate from the aneurysm sac but not over inflated because an overinflated balloon can rupture or can put undue pressure on the aneurysm walls. Furthermore, the balloon often does not mold or shape to the odd-shaped contours of the aneurysm leaving room for blood to continue flowing through the aneurysm. Elastic balloons have exhibited problems with respect to performance and have not been used endovascularly in some time.
Aneurysm liners are composed of a liner sac which is placed in the aneurysm and filled to occlude the aneurysm. Aneurysm liners are formed of a semi-permeable fabric and are expanded to conform to the shape of the aneurysm. Aneurysm liners are inserted in a low profile into an aneurysm sac. Once inserted, the liner can be radially expanded to form an inner cavity in the liner. The liner is radially expanded by filling the liner with embolic material. The liner can be attached to a catheter device to insert and deploy the liner in the aneurysm sac. The aneurysm liner is inserted intravascularly over a guidewire extending through a lumen in the liner. In such devices, the guidewire lumen should not form a passage for embolic material through the liner, since passage of embolic material through the liner can hinder the process of filling the liner with embolic material to occlude the aneurysm. The present invention addresses these and other problems.